Although both preclinical and clinical studies continue to document the chemopreventive activity of the nonsteroidal anti-inflammatory drug FGN-1 (Aptosyn, exisulind), its mechanism of action remains unclear. The hypothesis of the proposed experimentation is that FGN-1 induces apoptosis by decreasing both nuclear levels of beta-catenin and the transcriptional activation of downstream targets of the APC/beta-catenin pathway. The rationale for this hypothesis is provided by previous studies, which indicate that FGN-1 lacks cyclooxygenase inhibitory activity and induces apoptosis independent of p53, bcl-2, cell cycle arrest and decreased cell proliferation. The ability of FGN-1 to induce apoptosis in human colonic adenomas harboring mutations in the adenomatous polyposis coli (APC)gene when combined with the reported role of APC in apoptosis suggests that FGN-1 may restore the activity of a malfunctioned APC/beta-catenin pathway. Data from preliminary studies support this hypothesis and indicate that FGN-1 decreases both levels of nuclear beta-catenin and the expression of cyclin Dl, a downstream target of the APC/beta-catenin pathway, in cells with mutant APC. All experimentation will focus on colon carcinogenesis, where the role of APC has been investigated extensively and the antitumor activity of FGN-l has been well documented. In Aim 1, a unique strain of multiple intestinal neoplasia (Min) mice, bearing a mutation in the APC gene, will be utilized to evaluate the chemopreventive activity of FGN-l analogs (i.e., CP248), which may be more efficacious than the parent compound in inhibiting colon tumor formation. Drug-induced changes in the expression and interaction of APC,beta-catenin, Axin and GSK3beta, the phosphorylation of beta-catenin, and the expression of downstream targets of the APC/beta-catenin pathway will be systematically evaluated in Aim 2, using both colorectal tissues from Minmice and human colon carcinoma cell lines with defined mutations in APC and beta-catenin. In Aim 3, the ability of FGN-l/CP248 to modulate beta-catenin-regulated transcription will be confirmed using a Tcf reporter assay. These findings will be translated to a clinical setting in Aim 4, where the cellular distribution of beta-catenin will be examined in colon tissues from FAP patients before and after FGN-I administration. It is anticipated that the proposed preclinical experimentation will not only enhance our current understanding of the role of APC in apoptosis, but contribute to both the establishment of biomarkers of FGN-1 activity and the identification of novel cellular targets for chemopreventive intervention.